The objective of the proposed work is to understand the mechanism by which vitamins are distributed into different tissues with the egg yolk as the model system and biotin as the specific example. The working hypothesis is that the transport of vitamins is mediated by specific vitamin-binding glyco-proteins synthesized in the liver, transported by the blood stream and taken up by tissues which recognize specific structural features (e.g., attached carbohydrate) of the vitamin binding protein. A biotin-binding protein from egg yolk will be purified to homo geneity and characterized. Its properties will be compared to avidin, a well-characterized biotin-binding protein from egg white. BIBLIOGRAPHIC REFERENCES: Abstracts: Meslar, Harry W. et al. (1976) Fed. Proc. 35(7) abst. #970 "Biotin-Binding Protein from Chicken Egg Yolk". Meslar, H. W., S. A. Camper and H. B. White, III (1977) Fed. Proc. 36(3) abst. #2316 "Purification and Properties of Egg Yolk Biotin-Binding Protein".